JP2014225961A - Detector, power supply system and control method of detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a detector capable of correctly detecting a foreign matter in a magnetic field.SOLUTION: The detector includes: a measurement section and a foreign matter detection section. The measurement section measures a voltage from a measuring coil disposed in the vicinity of a power reception coil for receiving the power supplied via a magnetic field as measured coil voltage. The foreign matter detection section acquires at least one electric characteristic value from the power reception coil and the measuring coil based on the measured coil voltage, and when the electric characteristic value is smaller than a predetermined lower limit threshold, the foreign matter detection section detects a foreign matter in the magnetic field.

Description

  The present technology relates to a detection device, a power feeding system, and a control method for the detection device. Specifically, the present invention relates to a detection device that detects a foreign object in a magnetic field, a power feeding system, and a control method for the detection device.

  2. Description of the Related Art In recent years, a power supply system that supplies electric power in a contactless manner to CE (Consumer Electronics) devices such as a mobile phone and a portable music player has attracted attention. This power feeding system is called a non-contact power feeding system, a non-contact power transmission system, or a wireless power feeding system. With this system, the secondary device can be charged by a simple method such as placing a secondary device such as an electronic device on the primary device such as a power supply device. That is, terminal connection is not required between the electronic device and the power feeding device.

  An electromagnetic induction method is well known as a method for supplying power without contact in this manner. Recently, a non-contact power feeding system using a method called a magnetic field resonance method (or magnetic resonance method) using a resonance phenomenon has attracted attention.

  The non-contact power supply system using the magnetic field resonance method has an advantage that power can be transmitted between devices separated from each other by using the principle of resonance phenomenon, compared to the electromagnetic induction method. In addition, there is an advantage that the power transmission efficiency (that is, the power feeding efficiency) does not decrease much even if the axial alignment between the power feeding coil of the power feeding source and the power receiving coil of the power feeding destination is somewhat poor.

  However, both of the magnetic field resonance method and the electromagnetic induction method are still non-contact power supply systems that use magnetic coupling between a power supply source power supply coil and a power supply destination power reception coil.

  By the way, one of the important elements in the non-contact power supply system is a countermeasure against heat generation of foreign matters such as metal, magnetic material and magnet that can generate heat due to magnetic lines of force. In a non-contact power supply system using an electromagnetic induction method or a magnetic field resonance method, if a foreign object is mixed in the gap between the power feeding coil and the power receiving coil, the foreign object may generate heat due to magnetic lines passing through the foreign object. The heat generated by the foreign material is caused by eddy current loss that occurs in the metal foreign material when the magnetic line of force passes through the metal foreign material, or hysteresis loss that occurs in the magnetic material of the foreign material when the magnetic field line passes through the magnetic material or foreign magnet. ing.

  Since heat generation from a foreign material can lead to malfunction or damage of a power supply device or an electronic device, it can be said that prevention of heat generation from the foreign material is a major problem of the non-contact power supply system.

  As a countermeasure against this heat generation, there is a method to detect the heat generation of a foreign object by adding a temperature sensor, but this method detects a foreign object that has already become high temperature, so it is difficult to say that it is a drastic countermeasure method for heat generation of a foreign object. . That is, as a method for detecting a foreign object that can generate heat due to magnetic lines of force, a method that can detect the foreign object before it generates significant heat is desirable.

  Therefore, a method has been proposed in which the presence or absence of a metallic foreign object is determined by looking at changes in electrical parameters (such as current and voltage) when a metallic foreign object enters between the power supply side and the power receiving side. With such a method, the presence of foreign matter can be detected before it generates significant heat. Specifically, a method of detecting a metal foreign object by a change in amplitude and phase during communication between the power feeding side and the power receiving side has been proposed (see, for example, Patent Document 1). In addition, a method for detecting a metal foreign object by eddy current loss has been proposed (see, for example, Patent Document 2).

JP 2008-206231 A JP 2001-275280 A

  However, the above-described conventional technology may not be able to accurately detect foreign matter. In the above system, the influence of the metal housing on the power receiving side is not taken into consideration. When charging a general electronic device, there is a high possibility that some metal (such as a metal casing or a metal part) is used in the electronic device. For this reason, it is difficult to determine whether the change in the parameter is “because of the influence of the metal casing or the like” or “because of the contamination of the metal foreign matter”. For example, when a foreign object is detected by a change in eddy current loss, whether the eddy current loss is generated in the metal housing of the electronic device, or is generated by mixing a metal foreign object between the power feeding side and the power receiving side. I can't judge. The same applies when foreign matter is detected by changes in amplitude and phase.

  The present technology has been created in view of such a situation, and aims to accurately detect foreign matter in a magnetic field.

  The present technology has been made to solve the above-described problems. The first aspect of the present technology is a measurement coil disposed in the vicinity of a power receiving coil that receives power supplied via a magnetic field; A measurement unit that measures the voltage of the measurement coil as a measurement coil voltage, and obtains an electric characteristic value of at least one of the power receiving coil and the measurement coil based on the measurement coil voltage, and the electric characteristic value is less than a predetermined lower threshold If it is also small, there is a detection device including a foreign substance detection unit for detecting the foreign substance in the magnetic field, and a control method therefor. Thereby, when the electrical characteristic value is smaller than a predetermined lower limit threshold value, foreign matter is detected.

  In the first aspect, the foreign matter detection unit may detect the foreign matter when the electrical property value is smaller than the lower limit threshold value or when the electrical property value is larger than an upper limit threshold value greater than the lower limit threshold value. It may be detected. Thereby, when the electrical characteristic value is smaller than the lower limit threshold value or when the electrical characteristic value is larger than the upper limit threshold value, foreign matter is detected.

  In the first aspect, the measurement unit may be configured such that the upper limit threshold is a value greater than a reference value that is the electrical characteristic value when there is no foreign object, and the lower limit threshold is a value smaller than the reference value. It may be. This brings about the effect that foreign matter is detected when the electrical characteristic value is smaller than the lower limit threshold smaller than the reference value.

  In the first aspect, the measurement unit further measures the voltage and current of the power receiving coil, and the foreign object detection unit is configured to detect the voltage of the power receiving coil from the measurement coil voltage and the voltage and current of the power receiving coil. The impedance may be acquired as the electrical characteristic value. This brings about the effect that the impedance of the power receiving coil is acquired as an electrical characteristic value.

  In the first aspect, the measuring unit further measures the voltage of the power receiving coil as a power receiving coil voltage, and the foreign matter detecting unit calculates a voltage ratio between the measuring coil voltage and the power receiving coil voltage. It may be acquired as a characteristic value. This brings about the effect that the voltage ratio is acquired as the electrical characteristic value.

  In the first aspect, the measurement unit further measures the voltage of the power receiving coil as a power receiving coil voltage, and the power receiving coil sequentially receives the first and second powers having different power amounts, and The foreign object detection unit acquires, as the electrical characteristic value, a difference between the voltage ratio acquired when the first power is received and the voltage ratio acquired when the second power is received. Also good. Thereby, the effect that the difference of voltage ratio is acquired as an electrical characteristic value is brought about.

  In the first aspect, the measurement coil may be a coil having a coil surface area smaller than that of the power receiving coil. This brings about the effect | action that the voltage of a measurement coil whose area of a coil surface is smaller than a receiving coil is measured.

  In the first aspect, the measurement coil may be disposed inside the power receiving coil. This brings about the effect | action that the voltage of the measurement coil arrange | positioned inside a receiving coil is measured.

  In the first aspect, the measurement coil may be arranged on substantially the same plane as the power receiving coil. This brings about the effect | action that the voltage of the measurement coil arrange | positioned in the substantially same plane as a receiving coil is measured.

  In the first aspect, the measurement coil may be disposed at a position where the center of the power receiving coil and the coil surface substantially coincide. This brings about the effect that the voltage of the measuring coil arranged at the position where the center of the power receiving coil and the coil surface substantially coincide with each other is measured.

  In the first aspect, the power is power fed by a power feeding device, and when the foreign object is detected, a control signal requesting reduction of the power amount of the power is transmitted to the power feeding device. A transmission unit may be further included. Thereby, when a foreign object is detected, the effect that the control signal which requests | requires reduction of the electric energy of electric power is transmitted is brought about.

  In addition, a second aspect of the present technology includes a measurement coil disposed in the vicinity of a feeding coil that supplies power via a magnetic field, a measurement unit that measures the voltage of the measurement coil as a measurement coil voltage, and the measurement coil A foreign matter detection unit that obtains an electrical property value of at least one of the power receiving coil and the measurement coil based on a voltage and detects the foreign matter in the magnetic field when the electrical property value is smaller than a predetermined lower threshold; This is a detection device. Thereby, when the electrical characteristic value is smaller than a predetermined lower limit threshold value, foreign matter is detected.

  In addition, a third aspect of the present technology includes a power supply coil that supplies power via a magnetic field, a power reception coil that receives the power, a measurement coil that is disposed near the power reception coil, and a voltage of the measurement coil. A measurement unit that measures a voltage as a measurement coil voltage, and when the electrical property value of at least one of the power receiving coil and the measurement coil is acquired based on the measurement coil voltage and the current electrical property value is smaller than a predetermined lower threshold value Is a power supply system including a foreign matter detection unit for detecting the foreign matter in the magnetic field. This brings about the effect that foreign matter is detected based on the measurement coil voltage.

  According to the present technology, it is possible to obtain an excellent effect that foreign matters in a magnetic field can be accurately detected.

It is a perspective view which shows one structural example of the non-contact electric power feeding system in 1st Embodiment. It is a block diagram which shows the example of 1 structure of the electric power feeder in 1st Embodiment. It is a block diagram which shows one structural example of the power receiving apparatus in 1st Embodiment. It is a figure which shows an example of the receiving coil and detection coil in 1st Embodiment. It is a block diagram which shows one structural example of the foreign material detection part in 1st Embodiment. It is a flowchart which shows an example of operation | movement of the electric power feeder in 1st Embodiment. It is a flowchart which shows an example of operation | movement of the power receiving apparatus in 1st Embodiment. It is a graph which shows an example of the temperature change of the foreign material in 1st Embodiment. It is a graph which shows an example of a change of the impedance of a receiving coil in a 1st embodiment. It is a graph which shows an example of change of deltaK in a 2nd embodiment. It is a graph which shows an example of the change of the voltage ratio in 3rd Embodiment. It is a graph which shows an example of a change of voltage of a detection coil in a 4th embodiment. It is sectional drawing which shows the example of arrangement | positioning of the receiving coil and detection coil in a modification.

Hereinafter, modes for carrying out the present technology (hereinafter referred to as embodiments) will be described. The description will be made in the following order.
1. 1st Embodiment (example which detects a foreign material based on impedance)
2. Second Embodiment (Example of detecting foreign matter based on ΔK)
3. Third Embodiment (Example of detecting foreign matter based on voltage ratio)
4). Fourth Embodiment (Example of detecting foreign matter based on detection coil voltage)
5. Modified example

<1. First Embodiment>
[Configuration example of wireless power supply system]
FIG. 1 is a perspective view illustrating a configuration example of a contactless power feeding system according to an embodiment. This non-contact power supply system is a system for supplying electric power in a non-contact manner via a magnetic field. The non-contact power feeding system includes a power feeding device 100 and power receiving devices 400 and 401. Note that the number of power receiving devices is not limited to two, and may be one or three or more.

  The power feeding apparatus 100 supplies power to the power receiving apparatuses 400 and 401 by magnetic force in a non-contact manner. By non-contact power feeding, the user can perform charging with an easy operation such as placing the power receiving devices 401 and 401 on the power feeding device 100 without performing terminal connection to an AC (Alternating Current) adapter or the like. Such a charging method reduces the burden on the user.

  For example, the power supply apparatus 100 is formed in a shape having a plane with a constant area. Specifically, the power supply apparatus 100 has a shallow box shape (so-called tray shape), a rug-like shape (so-called mat shape), or a small and flat upper portion (so-called trapezoidal shape). Formed. A feeding coil that generates a magnetic field is disposed below and on the surface (hereinafter referred to as “feeding surface”).

  The plane of the power feeding surface is desirably sufficiently larger than the area of the power receiving surface of these devices so that a plurality of power receiving devices such as the power receiving devices 400 and 401 can be placed. Here, the power receiving surface is a plane in which a power receiving coil that receives power supplied via a magnetic field is arranged on the lower part or the surface. By placing a plurality of power receiving devices on the power feeding surface, the non-contact power feeding system can charge these devices simultaneously or sequentially.

  In addition, although it is set as the structure which makes the area of an electric power feeding surface larger than the area of a receiving surface, it is not limited to this structure. Those areas may be the same, or the area of the power feeding surface may be smaller than the power receiving surface. Further, since charging can be performed only by bringing the power receiving device 400 or the like close to each other, the shape of the power feeding device 100 is not limited to a shape having a flat surface. For example, the power supply apparatus 100 may have a stand shape such as a desktop holder or a cradle.

  Further, although the power supply apparatus 100 is configured to perform only charging, bidirectional data transfer may be performed between the power receiving apparatus 400 and the power receiving apparatus 400.

  The power receiving apparatus 400 receives power supplied from the power supply apparatus 100 via a magnetic field. For example, an electronic device such as a mobile phone terminal or an electronic still camera is used as the power receiving device 400. The power receiving apparatus 400 detects the presence or absence of a foreign substance in the magnetic field, and if there is a foreign substance, the power receiving apparatus 400 requests the power supply apparatus 100 to reduce the amount of power supplied. The power supply apparatus 100 reduces the amount of power supply in response to the request. Thereby, the heat generation of the foreign matter is prevented. The configuration of the power receiving device 401 is the same as that of the power receiving device 400.

  Note that the power receiving device 400 may be a device other than an electronic device such as an electric vehicle. In the case of an electric vehicle, the power receiving device 400 can detect, for example, a metal foreign object adhering to the vehicle body mixed with mud or the like.

[Configuration example of power supply device]
FIG. 2 is a block diagram illustrating a configuration example of the power supply apparatus 100 according to the first embodiment. The power supply apparatus 100 includes a power conversion circuit 110, a power supply control unit 120, a demodulation circuit 130, an impedance matching circuit 140, a capacitor 150, and a power supply coil 160.

  The power conversion circuit 110 is a circuit that converts the voltage and frequency of power supplied from an external power supply source of the power supply apparatus 100 to generate AC power for performing power transmission. The power conversion circuit 110 changes the frequency of the AC power to be generated when the power supply control unit 120 instructs to change the frequency. Here, the external power supply source is, for example, a commercial power source supplied via a plug socket (so-called outlet).

  The power supply control unit 120 controls the amount of power supplied to the power receiving device 400. When the power supply device 100 is turned on, the power supply control unit 120 controls the power conversion circuit 110 to cause the power receiving device 400 to start supplying a predetermined amount of power W1. Here, the power amount W1 is set to, for example, the minimum power amount at which the power receiving apparatus 400 can operate.

  Then, the power supply control unit 120 receives a power supply control signal for controlling the power supply amount from the power receiving apparatus 400 via the demodulation circuit 130. The power supply control unit 120 controls the power supply amount according to the power supply control signal. This power supply control signal includes, for example, a signal that requests an increase in the amount of power supply and a signal that requests a decrease in the amount of power supply.

  When an increase in the power supply amount is requested, the power supply control unit 120 controls the power conversion circuit 110 to cause the power receiving apparatus 400 to supply a power amount W2 higher than the power amount W1. Here, the power amount W2 is set to a power amount sufficient for the power receiving apparatus 400 to charge the secondary battery, for example.

  Then, when a reduction in power supply amount is requested when the power amount is W2, the power supply control unit 120 controls the power conversion circuit 110 to return the power amount to W1. In addition, although the electric power feeding control part 120 is controlling the electric energy in two steps, W1 and W2, you may control in three steps or more, and may control the start and stop of electric power feeding.

  Control of the power supply amount is realized, for example, when the power supply control unit 120 controls the power conversion circuit 110 to change the AC frequency. Specifically, the power supply control unit 120 substantially matches the AC frequency to a specific frequency (for example, a resonance frequency) when increasing the power supply amount, and sets the AC frequency to a specific frequency when decreasing the power supply amount. And control to a different value.

  In addition, control of electric power feeding amount is not limited to the change of AC frequency. For example, the power supply control unit 120 may control the power supply amount by causing the power conversion circuit 110 to step down or boost the AC voltage. When the power conversion circuit 110 is configured to generate a pulse signal from a switching power supply or the like and supply the pulse signal to the power supply coil 160, the power supply control unit 120 controls the power supply amount by changing the duty ratio of the pulse signal. Also good.

  The demodulation circuit 130 demodulates the AC signal from the power receiving device 400 and extracts a power supply control signal superimposed on the AC signal. The demodulation circuit 130 supplies the power supply control signal to the power supply control unit 120.

  The impedance matching circuit 140 is a circuit that matches the impedance of the circuit on the power receiving side by controlling the impedance of the circuit on the power feeding side. Impedance matching improves power transmission efficiency. When the transmission efficiency is sufficiently high or when the transmission efficiency is sufficiently improved only by impedance matching on the power receiving side, the impedance matching circuit 140 may not be provided.

  The capacitor 150 is an element that stores or emits electrical energy. The capacitor 150 is connected to the feeding coil 160 in series, for example, and constitutes an LC resonance circuit together with the feeding coil 160. The capacitance value of the capacitor 150 is set so that the resonance frequency f1 of the LC resonance circuit substantially coincides with the resonance frequency f2 of the LC resonance circuit on the power receiving side, or the frequency close to the resonance frequency f2.

  Note that the capacitor 150 is not provided if the resonance frequency f1 can be obtained by a parasitic capacitance component including a line capacitance in the feeding coil 160, a capacitance between the feeding coil 160 and a power receiving coil described later, and the like. It is good also as a structure. Further, when the power transmission efficiency is sufficiently high, the capacitor 150 may not be provided.

  The capacitor 150 may be a variable capacitance capacitor. In that case, the power feeding control unit 120 adjusts the resonance frequency by controlling the capacitance.

  When AC power is supplied from the power conversion circuit 110, the power feeding coil 160 generates electromagnetic waves according to Ampere's law. Power is supplied to the power receiving device 400 via this electromagnetic wave.

  In addition, although the power supply apparatus 100 is configured to include one power supply coil 160, the power supply device 100 may be configured to include a plurality of power supply coils 160.

[Configuration example of power receiving device]
FIG. 3 is a block diagram illustrating a configuration example of the power receiving device 400 according to the first embodiment. The power receiving device 400 includes a detection coil 410, a capacitor 420, a power receiving coil 430, capacitors 440 and 441, and a power reception control unit 450. The power receiving apparatus 400 includes a charge control unit 480, a secondary battery 481, and a load circuit 482.

  The detection coil 410 is a coil that is disposed in the vicinity of the power reception coil 430 and that measures a voltage in order to detect foreign matter. The detection coil 410 is an example of a measurement coil described in the claims.

  The capacitor 420 is an element that stores or emits electrical energy. The capacitor 420 is connected to the detection coil 410, for example, in series. The capacitor 420 is used for a resonance application, a filter application, a coupling application, and the like. In particular, in the case of resonance use, an LC resonance circuit is configured together with the detection coil 410. In the LC resonance circuit, the capacitance value of the capacitor 420 is set so that the resonance frequency is f3. In addition, this resonance frequency f3 is desirably set so as not to coincide with the resonance frequency f1 on the power supply side when it is desired to reduce electromagnetic interference caused by the power supply side. On the other hand, when it is desired to actively use electromagnetic interference caused by the power supply side, it may be substantially matched with the resonance frequency f1 on the power supply side. Of course, the capacitor 420 is not necessarily provided if there is no need for a resonance application, a filter application, or a coupling application.

  The power receiving coil 430 receives power supplied from the power supply apparatus 100. Specifically, when an electromagnetic wave is supplied from the power supply apparatus 100, the power receiving coil 430 generates an induced voltage according to a change in the magnetic flux of the electromagnetic wave in accordance with the law of electromagnetic induction.

  Note that the power receiving device 400 includes one power receiving coil 430, but may include a plurality of power receiving coils 430. When a plurality of power receiving coils 430 are provided, the detection coil 410 is disposed in the vicinity of at least one of the power receiving coils 430.

  Capacitors 440 and 441 are elements that store or emit electrical energy. The capacitor 440 is connected in series to the power receiving coil 430, and the capacitor 441 is connected to the power receiving coil 430 in parallel. These capacitors 440 and 441 form an LC resonance circuit together with the power receiving coil 430. The capacitance value of the capacitor 440 and the like is set so that the resonance frequency f2 of the LC resonance circuit is substantially the same as the resonance frequency f1 on the power supply side or a frequency in the vicinity of the resonance frequency f1.

  Note that at least one of the capacitors 420 and 440 may be a variable capacitance capacitor. In that case, the power reception control unit 450 adjusts the resonance frequency by controlling the capacitance. On the other hand, if the resonance frequency f2 can be obtained by the line capacitance in the receiving coil 430, the parasitic capacitance component composed of the capacitance between the feeding coil 160 and the receiving coil 430 described above, the capacitor 420 and the capacitor A configuration without 440 may also be employed. Further, when the power transmission efficiency is sufficiently high, the capacitor 420 or the capacitor 440 may be omitted.

  In addition to the resonance circuit including the detection coil 410 and the resonance circuit including the power reception coil 430, the power reception device 400 may further include a resonance circuit.

  The power reception control unit 450 controls the entire power reception device 400. The power reception control unit 450 includes a measurement unit 451, a foreign object detection unit 460, a modulation circuit 452, a power reception control circuit 453, an impedance matching circuit 454, a rectification circuit 455, a voltage stabilization circuit 456, and a load connection circuit 457.

  The power reception control unit 450 includes terminals 471, 472, 473, and 474. One end of the detection coil 410 is connected to the terminal 471 through the capacitor 420. The terminals 472 and 473 are connected to an LC resonance circuit including the power receiving coil 430. A charging control unit 480 is connected to the terminal 474.

The measurement unit 451 measures the voltage V ₂ and current I ₂ of the power receiving coil 430 and the voltage V ₃ of the detection coil 410. The voltage is measured by an instrument transformer. The current is obtained from, for example, a potential difference between both ends of a shunt resistor connected in series to the power receiving coil. In the measurement, for example, volt (V) is used as a unit of voltage, and for example, ampere (A) is used as a unit of current.

  The current may be obtained with a current transformer. Further, the measurement unit 451 may include an amplifier circuit that amplifies the AC signal, and may measure a voltage amplified by the amplifier circuit. The measurement unit 451 can measure the voltage and the like with high accuracy by the amplification of the AC signal.

The voltage V ₂ of the power receiving coil 430 is hereinafter referred to as “power receiving coil voltage”, and the current I ₂ of the power receiving coil 430 is hereinafter referred to as “power receiving coil current”. Further, the voltage V ₃ of the sensing coil hereinafter referred to as "sensing coil voltage". The measurement unit 451 supplies these measurement values to the foreign object detection unit 460.

  Here, the power receiving coil voltage and the power receiving coil current to be measured are voltages and currents before being rectified by the rectifier circuit 455. Note that the measurement unit 451 may measure the receiving coil voltage and the receiving coil current after rectification.

  The foreign matter detection unit 460 detects foreign matter in the magnetic field from the power supply apparatus 100 based on the measurement value measured by the measurement unit 451. The foreign object detection unit 460 determines whether a load is connected based on a connection control signal from the power reception control unit 450. And the foreign material detection part 460 acquires the measured value in each when a load is connected, and when a load is unconnected, and detects a foreign material based on those measured values. Details of the detection method will be described later. The foreign object detection unit 460 supplies the detection result of the foreign object to the power reception control unit 450.

  The device including the detection coil 410, the measurement unit 451, and the foreign object detection unit 460 is an example of the foreign object detection device described in the claims. In addition, although the foreign object detection device is built in the power receiving device 400, the foreign object detection device may be provided outside the power receiving device 400.

  The modulation circuit 452 superimposes the power supply control signal by modulating the amplitude of the AC signal to the power supply apparatus 100 and the like. When receiving a power supply control signal from the power reception control circuit 453, the modulation circuit 452 superimposes the power supply control signal on the AC signal. As a result, a power supply control signal is transmitted to the power supply apparatus 100.

  Note that although the modulation circuit 452 performs load modulation, the modulation may be performed by a modulation method other than load modulation. Moreover, although the power receiving apparatus 400 is transmitting the power feeding control signal by load modulation, it may be transmitted by other methods. For example, the power receiving apparatus 400 may further include a communication coil and an antenna, and may use them to transmit a power supply control signal.

  The power reception control circuit 453 controls the power supply amount based on the foreign object detection result. The power reception control circuit 453 supplies a connection control signal instructing disconnection of the load to the load connection circuit 457 when the power of the electric power W1 is supplied from the power supply apparatus 100.

  When the measurement end notification is received from the foreign object detection unit 460, the power reception control circuit 453 supplies a connection control signal for instructing connection of the load to the load connection circuit 457, and modulates the power supply control signal for requesting an increase in power supply amount. Supply to circuit 452. As a result, the power supply amount increases from W1 to W2.

  Upon receiving a detection result indicating that a foreign object has been detected after the power amount W2 is supplied, the power reception control circuit 453 supplies a connection control signal instructing disconnection of the load to the load connection circuit 457, and the power supply amount Is supplied to the modulation circuit 452. As a result, the power supply amount is reduced from W2 to W1, and the heat generation of the foreign matter is suppressed.

  Note that the power reception control circuit 453 requests that the power supply amount be returned to the initial W1 when the foreign object is detected, but may be configured to request the power supply amount to be lower than W1 when the foreign object is detected. The power reception control circuit 453 may request a power supply amount that is lower than W2 but higher than W1 when foreign matter is detected. Alternatively, the power reception control circuit 453 may be configured to request power supply stop when detecting a foreign object. Alternatively, the power reception control circuit 453 may be configured to instruct only the disconnection of the load at the time of detecting a foreign object and does not request a reduction in the amount of power supply. In the case where reduction of the amount of power supply is not required, the modulation circuit 452 is not necessary. In addition, the power reception control circuit 453 disconnects the load when the foreign object is detected, but may be configured to request a reduction in the amount of power supply while the load is connected when the foreign object is detected.

  In addition, the power reception control circuit 453 transmits only the power supply control signal, but may transmit a foreign object detection result separately from the power supply control signal. In this case, the power supply apparatus 100 may reduce the power supply amount when detecting a foreign object.

  In addition, the power reception control circuit 453 controls the rectifier circuit 455 and the voltage stabilization circuit 456. For example, the power reception control circuit 453 operates the rectifier circuit 455 and the voltage stabilization circuit 456 when the power amount W2 is supplied, and stops them when a foreign object is detected.

  The impedance matching circuit 454 is a circuit that matches the impedance of the power supply side circuit by controlling the impedance of the power reception side circuit. Impedance matching improves power transmission efficiency. Note that the impedance matching circuit 454 may be omitted when the transmission efficiency is sufficiently high or when the transmission efficiency is sufficiently improved only by impedance matching on the power feeding side.

  The rectifier circuit 455 rectifies the AC power supplied from the power supply apparatus 100 to generate DC power. The rectifier circuit 455 supplies the generated DC power to the charge control unit 480 via the voltage stabilization circuit 456 and the load connection circuit 457. The voltage stabilization circuit 456 controls the DC power voltage to be constant.

  Note that the power after rectification by the rectifier circuit 455 is supplied to the voltage stabilization circuit 456 as it is, but the configuration is not limited thereto. For example, a configuration may be employed in which a smoothing circuit that smoothes the power after rectification is provided between the rectification circuit 455 and the voltage stabilization circuit 456.

  The load connection circuit 457 controls the load connected state or the load disconnected state according to the control of the power reception control circuit 453. Specifically, when the load connection circuit 457 is instructed to disconnect the load, the load connection circuit 457 opens the electric circuit between the rectification circuit 455 and the charge control unit 480 and cuts off the supply of DC power. On the other hand, when the connection of the load is instructed, the load connection circuit 457 closes the electric circuit between the rectifier circuit 455 and the charge control unit 480.

  The charging control unit 480 charges the secondary battery 481 by controlling the voltage and current of DC power. Further, the charging control unit 480 supplies a part of the charging power to the load circuit 482 while the secondary battery 481 is being charged. The secondary battery 481 stores the power charged by the charging control unit 480. For example, a lithium ion battery or the like is used as the secondary battery 481. The load circuit 482 is a circuit that operates using power from the secondary battery 481 or the charging control unit 480.

  Note that although the charge control unit 480 is provided outside the power reception control unit 450, the charge control unit 480 may be built in the power reception control unit 450. Thereby, the power reception control unit 450 can effectively limit or stop power supply to the secondary battery 481 and the load circuit 482. In that case, the charging control unit 480 may be incorporated in the power reception control circuit 453. On the other hand, the charge control unit 480 may be configured to control at least a part of the power reception control unit 450 while the charge control unit 480 is provided outside the power reception control unit 450.

  Further, although the foreign object detection device is provided on the power receiving side, the foreign object detection device may be provided on the power supply side instead of the power reception side. In this case, the detection coil 410 is disposed in the vicinity of the power supply coil 160, and the foreign object detection unit 460 detects a foreign object in the magnetic field generated by the power supply coil 160. In addition, the foreign object detection device is provided inside or outside the power supply device 100. Moreover, you may provide a foreign material detection apparatus in both the electric power feeding side and a power receiving side.

  In addition to the configurations illustrated in FIGS. 2 and 3, the power feeding device 100 and the power receiving device 400 may further include a circuit or the like as necessary. For example, at least one of the power supply device 100 and the power reception device 400 includes a display unit that displays a foreign object detection result, a communication unit that performs bidirectional communication, and whether or not the power reception device 400 is placed on the power supply device 100. You may further provide the detection part etc. which detect.

  FIG. 4 is a diagram illustrating an example of the power reception coil 430 and the detection coil 410 according to the first embodiment. 4A is an example of a plan view of the power receiving coil 430 and the detection coil 410. FIG.

  The area of the coil surface of the detection coil 410 is smaller than the power receiving coil 430. The detection coil 410 is disposed inside the power receiving coil 430. Further, it is desirable that the detection coil 410 be arranged so that the center thereof substantially coincides with the center of the power receiving coil 430.

  4B is an example of a cross-sectional view of the power reception coil 430 and the detection coil 410 taken along line A-B in FIG. 4A. In order to reduce the thickness of the device as illustrated in b in the figure, and from the viewpoints of mountability and mass productivity, it is desirable that the detection coil 410 and the power receiving coil 430 be disposed on substantially the same plane.

  In FIG. 4b, the detection coil 410 and the power receiving coil 430 are arranged on substantially the same plane, but they may be arranged on different planes.

  The power receiving coil 430, the detection coil 410, and the power feeding coil 160 are formed by, for example, winding a conductive wire, and the number of windings is arbitrary. In addition, you may form these coils by methods other than the method of winding an electroconductive wire. For example, a conductive pattern may be formed on a printed wiring board or a flexible printed board. Such a coil is called a pattern coil or a pattern loop. The pattern coil can also be formed by printing or vapor-depositing a conductive material on a substrate, or processing a conductive sheet metal or sheet.

  Moreover, you may comprise these coils by the winding method which winds the wire which bundled two or more electroconductive strands. Specifically, it is constituted by a winding method of winding a wire in which two conductive wires are bundled or a winding method of winding a winding in which three of the wires are bundled. The former is called bifilar winding, and the latter is called trifilar winding. Moreover, the winding of each coil may be a wire rod (that is, a litz wire) in which a plurality of conductive strands are bundled and twisted.

  Moreover, as these coils, you may use the coil of the helical shape in which the winding is wound in the spiral shape or thickness direction. Further, each coil may be formed by an α winding shape in which a spiral coil is arranged so as to be folded back in two layers, a further multilayer spiral shape, or the like.

  Further, a shield made of a magnetic material, a magnet, a conductor, or a metal may be provided around these coils for the purpose of preventing magnetic flux leakage and improving transmission efficiency.

  Further, the detection coil 410 may be provided inside a portion (that is, a track) around which the winding of the power receiving coil 430 is wound. Furthermore, a coil used for applications other than non-contact power feeding, such as an induction heating coil or a wireless communication coil, may be used in combination as the detection coil 410. In addition, the power receiving coil 430 may be used as the detection coil 410 depending on the configuration of the non-contact power feeding system. In addition to the case where the same coil is used in combination, these combinations are also assumed when a part of the coil is used together by switching or the like.

  If there is a conductive foreign material such as metal in the magnetic field from the power supply apparatus 100, an eddy current is generated in the foreign material due to the electromagnetic induction effect. The foreign matter generates heat due to the Joule heat generated by the eddy current. Further, the magnetic field generated by the eddy current acts on the detection coil 410 and the power receiving coil 430, and changes electrical characteristics such as impedance in their equivalent circuits.

  In particular, when a foreign object is in the vicinity of the winding of the power receiving coil 430, the magnetic field near the winding is dispersed by the magnetic field generated by the foreign object, and the impedance of the equivalent circuit of the power receiving coil 430 increases. On the other hand, if the foreign object is near the center of the power receiving coil 430, the magnetic field concentrates near the center and the impedance of the power receiving coil 430 is reduced by the same principle as when the iron core is placed in the center of the power receiving coil 430. For this reason, the power receiving apparatus 400 can detect a foreign substance from the fluctuation | variation of the impedance made into the reference value the impedance when there is no foreign substance.

[Configuration example of foreign object detection unit]
FIG. 5 is a block diagram illustrating a configuration example of the foreign matter detection unit 460 according to the first embodiment. The foreign matter detection unit 460 includes a signal processing unit 461, a measurement value holding unit 462, an electrical characteristic acquisition unit 463, and a comparison unit 464.

The signal processing unit 461 performs predetermined signal processing on the measurement value. Specifically, separation of the real component and the imaginary component of the AC signal is performed as signal processing. The signal processing unit 461 _{causes the} measured value holding unit 462 to hold the receiving coil current I _2off measured when the load is not connected. Further, the signal processing unit 461 _causes the measured value holding unit 462 to hold the respective real number components of the power receiving coil voltage V _2off and the detection coil voltage V _3off measured when the load is not connected. When the signal processing unit 461 holds each measurement value when the load is not connected, the signal processing unit 461 generates a measurement end notification and supplies the measurement end notification to the power reception control circuit 453.

When the load is connected, the signal processing unit 461 _{causes the} measured value holding unit 462 to hold the _power receiving coil current I _2on measured at that time. Further, the signal processing unit 461 _causes the measured value holding unit 462 to hold the respective real number components of the power receiving coil voltage V _2on and the detection coil voltage V _3on measured when the load is connected. The measured value holding unit 462 holds a measured value.

  Note that the signal processing unit 461 may further execute a process of separating only the fundamental component from the harmonic component and noise component and extracting only the fundamental component as signal processing. Further, the signal processing unit 461 may further execute processing for acquiring information on the carrier frequency and information on the duty ratio of the carrier and notifying the power reception control circuit 453. Further, when the measurement unit 451 is configured to measure a DC voltage or the like, it is not necessary for the signal processing unit 461 to separate the real number component and the imaginary number component.

The electrical characteristic acquisition unit 463 acquires a parameter indicating the electrical characteristics of at least one of the power receiving coil 430 and the detection coil 410 from the measured value. The electrical characteristic acquisition unit 463 acquires, for example, the impedance of the power receiving coil 430 on the equivalent circuit as a parameter. Specifically, the electrical characteristic acquisition unit 463 _reads the receiving coil currents I _2on and I _2off , the receiving coil voltages V _2on and V _2off, and the detection coil voltages V _3on and V _3off from the measurement value holding unit 462. . Then, the electric characteristic obtaining unit 463 obtains the resistance R ₂ as the impedance of the power receiving coil 430 from the measured values using the equations 1 to 4 follows. The electrical characteristic acquisition unit 463 supplies the obtained resistance R ₂ to the comparison unit 464.

Here, Equation 1 is derived from (R ₂ + R _on ) × I _{2on ≈real} (V _2on ) and (R ₂ + R _off ) × I _{2off ≈real} (V _2off ). In these equations, R _on is a real part of the impedance of a circuit that is substantially connected to the power receiving coil 430 when the load is connected, and R _off is a circuit that is substantially connected to the power receiving coil 430 when the load is not connected. The real part of the impedance. In Equations 1, 3, and 4, real (A) is a function that returns the real component of A.

  In Equations 3 and 4, the ratio of the real number component is obtained, but the ratio of the imaginary number component and the ratio of the absolute value may be obtained instead of the ratio of the real number component.

The electrical characteristic acquisition unit 463 is seeking a resistor R ₂ as the impedance of the power receiving coil 430, may be determined reactance of the power receiving coil 430 in place of the resistor.

  The comparison unit 464 compares the parameter acquired by the electrical characteristic acquisition unit 463 with the upper and lower thresholds. Here, the upper limit threshold value is set to a value larger than the reference value with the parameter value when there is no foreign matter as a reference value. Further, the lower limit threshold is set to a value smaller than the reference value. The comparison unit 464 detects a foreign object when the parameter is larger than the upper threshold or when the parameter is smaller than the lower threshold. The comparison unit 464 supplies the foreign object detection result to the power reception control circuit 453.

  In addition, although the foreign material detection part 460 has acquired each measured value of the electric power feeding amount at the time of connecting a load, and the electric power feeding amount at the time of non-connecting, it is not limited to this structure. For example, the power receiving apparatus 400 sequentially supplies two different amounts of power while the load is connected or the load is not connected, and the foreign matter detection unit 460 sequentially acquires the measurement values at the power supply amount. May be. In this case, the power receiving apparatus 400 does not need the load connection circuit 457 in measurement, but it is desirable to provide the load connection circuit 457 in the power receiving apparatus 400 from the viewpoint of operation and safety.

[Example of operation of power feeding device]
FIG. 6 is a flowchart illustrating an example of the operation of the power supply apparatus 100 according to the first embodiment. This operation starts, for example, when an external power source is turned on to the power supply apparatus 100. The power supply apparatus 100 supplies the minimum amount of power W1 via the magnetic field (step S901).

  Then, the power supply apparatus 100 determines whether or not an increase in the amount of power supply is requested by the power supply control signal (step S902). If an increase in the amount of power supply is not requested (step S902: No), the power supply apparatus 100 returns to step S902.

  If an increase in power supply amount is requested (step S902: Yes), the power supply apparatus 100 increases the power supply amount to W2 (step S903). Then, the power supply apparatus 100 determines whether or not a reduction in the amount of power supply is requested by the power supply control signal (step S904). If the reduction of the power supply amount is not requested (step S904: No), the power supply apparatus 100 returns to step S904.

  If reduction of the power supply amount is requested (step S904: Yes), the power supply apparatus 100 reduces the power supply amount to W1 (step S905) and returns to step S902.

[Operation example of power receiving device]
FIG. 7 is a flowchart illustrating an example of the operation of the power receiving device 400 according to the first embodiment. This operation starts when power is supplied from the power supply apparatus 100, for example. The power receiving apparatus 400 causes the load to be disconnected by the connection control signal (step S951). The power receiving apparatus 400 _{measures the power} receiving coil current I _2off , the power receiving coil voltage V _2off , and the detection coil voltage V _3off (step S952).

And the power receiving apparatus 400 makes the load connected by the connection control signal, and increases the power supply amount by the power supply control signal (step S953). The power receiving apparatus 400 _{measures the power} receiving coil current I _2on , the power receiving coil voltage V _2on , and the detection coil voltage V _3on (step S954). The power receiving apparatus 400 acquires a parameter of electrical characteristics from the measured value using Equation 1 or the like (step S956). The power receiving apparatus 400 determines whether or not the parameter is higher than the upper limit threshold (step S957).

  If the parameter is equal to or less than the upper limit threshold (step S957: No), the power receiving apparatus 400 determines whether the parameter is smaller than the lower limit threshold (step S958). When the parameter is larger than the upper limit threshold (step S957: Yes), or when the parameter is smaller than the lower limit threshold (step S958: Yes), the power receiving apparatus 400 detects a foreign object (step S959). Then, the power receiving apparatus 400 reduces the power supply amount by the power supply control signal (step S960). When the parameter is larger than the lower limit threshold (step S958: No), or after step S960, the power receiving apparatus 400 ends the operation for detecting a foreign object.

  Note that the power receiving apparatus 400 is configured to execute the detection process illustrated in FIG. 8 only once at the time of power reception, but the detection process may be periodically executed.

  FIG. 8 is a graph illustrating an example of a temperature change of the foreign matter in the first embodiment. The vertical axis in the figure is the temperature of the metal foreign object that generates heat due to the magnetic lines of force from the power supply apparatus 100, and the horizontal axis is the amount of deviation between the center of the foreign object and the center of the power receiving coil 430. The unit of temperature is, for example, ° C., and the unit of deviation is millimeter (mm). It is assumed that the winding of the power receiving coil 430 is disposed at a position around −13 mm from the center of the power receiving coil 430. As the amount of deviation approaches from -30 mm to 0 mm, the temperature of the foreign matter rises and becomes highest at around -13 mm. Also, when the amount of deviation is near 0 mm, the temperature is lower than the peak, but is higher than when it is −30 mm. From this, it can be seen that when there is a foreign substance inside the power receiving coil 430, the temperature of the foreign substance becomes relatively high. Therefore, for example, an allowable value of a temperature at which the power receiving device 400 is not damaged is determined, and a range in which the foreign matter generates heat (−20 mm to 0 mm, etc.) above that temperature is set as a range in which the foreign matter is to be detected. The power receiving device 400 is designed so that it can be detected.

  FIG. 9 is a graph illustrating an example of a change in impedance of the power receiving coil 430 according to the first embodiment. The vertical axis in the figure is the impedance of the power receiving coil 430, and the horizontal axis is the amount of deviation between the center of the foreign matter and the center of the power receiving coil 430. In FIG. 9, it is assumed that the measurement conditions such as the size and material of the foreign matter and the power supply amount are the same as those in FIG.

  As shown in FIG. 9, the impedance of the power receiving coil 430 is higher than the reference value near the track of the power receiving coil, and lower than the reference value near the center. For this reason, by setting the upper limit threshold Th_UR2 larger than the reference value and the lower limit threshold Th_LR2 smaller than the reference value to appropriate values, the power receiving device 400 is near the track or near the center where foreign matter generates heat at a temperature higher than the allowable value. Can accurately detect foreign objects.

  As described above, according to the first embodiment of the present technology, the power receiving device detects a foreign object when the impedance is smaller than the lower limit threshold, and thus detects the foreign object near the center of the power receiving coil 430 with high accuracy. be able to. Further, since the power receiving device detects the foreign matter when the impedance is larger than the upper limit threshold, the foreign matter can be detected with high accuracy in the vicinity of the track of the power receiving coil 430.

<2. Second Embodiment>
In the first embodiment, the power receiving apparatus 400 detects foreign matter from the impedance of the power receiving coil 430, but may detect foreign matter from ΔK. The power receiving device 400 according to the second embodiment is different from the first embodiment in that a foreign object is detected from ΔK.

Measuring portion 451 of the second embodiment does not measure the receiving coil current I _2. For this reason, an ammeter or the like is not required in the measurement unit 451.

  Further, the foreign object detection unit 460 of the second embodiment obtains ΔK using Expressions 2 to 4, and detects the foreign object by comparing the ΔK with a threshold value.

  FIG. 10 is a graph illustrating an example of a change in ΔK in the second embodiment. In the drawing, the vertical axis represents ΔK, and the horizontal axis represents the amount of deviation between the center of the foreign matter and the center of the power receiving coil 430. In FIG. 10, it is assumed that the measurement conditions such as the size and material of the foreign matter and the amount of power supply are the same as those in FIG.

  As shown in FIG. 10, ΔK of the power receiving coil 430 is higher than the reference value near the track of the power receiving coil, and lower than the reference value near the center. For this reason, by setting the upper limit threshold Th_UΔK larger than the reference value and the lower limit threshold Th_LΔK smaller than the reference value to appropriate values, the power receiving device 400 is near the track or near the center where foreign matter generates heat at a temperature higher than the allowable value. Can accurately detect foreign objects.

  Thus, according to the second embodiment, a foreign object can be accurately detected based on ΔK.

<3. Third Embodiment>
In the first embodiment, the power receiving apparatus 400 detects foreign matter from the impedance of the power receiving coil 430, but may detect foreign matter from the voltage ratio between the power receiving coil 430 and the detection coil 410. The power receiving device 400 according to the third embodiment is different from the first embodiment in that a foreign object is detected from the voltage ratio.

Measuring portion 451 of the third embodiment does not measure the receiving coil current I _2. For this reason, an ammeter or the like is not required in the measurement unit 451. The measurement unit 451, the load is not measured receiving coil voltage _{V 2off} and the sensing coil voltage _{V 3Off} when disconnected. Since these need not be measured, the latency from the start of measurement of measured values to the end of foreign object detection is shortened.

  In addition, the foreign object detection unit 460 of the third embodiment obtains a voltage ratio using Expression 4, and detects the foreign object by comparing the voltage ratio with a threshold value.

  FIG. 11 is a graph illustrating an example of a change in voltage ratio in the third embodiment. The vertical axis of the figure is the voltage ratio obtained from Equation 4, and the horizontal axis is the amount of deviation between the center of the foreign object and the center of the power receiving coil 430. In FIG. 11, it is assumed that the measurement conditions such as the size and material of the foreign matter and the amount of power supply are the same as those in FIG.

  As shown in FIG. 11, the voltage ratio of the power receiving coil 430 is higher than the reference value near the track of the power receiving coil, and is lower than the reference value near the center. For this reason, by setting the upper limit threshold Th_UR larger than the reference value and the lower limit threshold Th_LR smaller than the reference value to appropriate values, the power receiving apparatus 400 is near the track or near the center where foreign matter generates heat at a temperature higher than the allowable value. Can accurately detect foreign objects.

  Thus, according to the third embodiment, a foreign object can be accurately detected based on the voltage ratio.

<4. Fourth Embodiment>
In the first embodiment, the power receiving apparatus 400 detects foreign matter from the impedance of the power receiving coil 430, but may detect foreign matter from the detection coil voltage. The power receiving device 400 of the fourth embodiment _differs from the first embodiment in that a foreign object is detected from the detection coil voltage _V3on .

The measurement unit 451 of the fourth embodiment measures only the detection coil voltage _V3on . Moreover, since it is not necessary to measure a receiving coil voltage and an electric current, the structure of the measurement part 451 becomes simple.

Moreover, the foreign material detection part 460 of 3rd Embodiment detects a foreign material by comparing the real number component of the detection coil voltage _V3on , and a threshold value.

In addition, although the foreign material detection part 460 has detected the foreign material from the real component of the detection coil voltage _V3on , it is not limited to this structure. For example, foreign object detection section 460 may detect the foreign matter from the absolute value of the imaginary component and the sensing coil voltage V _3On detector coil voltage _V 3on.

FIG. 12 is a graph illustrating an example of a change in the detection coil voltage _V3on in the fourth embodiment. The vertical axis in the figure is the real component of the detection coil voltage V _3on , and the horizontal axis is the amount of deviation between the center of the foreign matter and the center of the power receiving coil 430. In FIG. 12, it is assumed that the measurement conditions such as the size and material of the foreign matter and the amount of power supply are the same as those in FIG.

As shown in FIG. 12, the detection coil voltage V _3on of the power receiving coil 430 is higher than the reference value near the track of the power receiving coil, and lower than the reference value near the center. For this reason, by setting the upper limit threshold Th_UV3 larger than the reference value and the lower limit threshold Th_LV3 smaller than the reference value to appropriate values, the power receiving apparatus 400 near the track or near the center where foreign matter generates heat at a temperature higher than the allowable value. Can accurately detect foreign objects.

  Thus, according to the fourth embodiment, a foreign object can be accurately detected based on the detection coil voltage.

[Modification]
In the first embodiment, the detection coil 410 is arranged in the layout illustrated in FIG. 4, but the detection coil 410 may be arranged in a layout different from that in FIG. 4. The power receiving device 400 according to the modified example is different from the first embodiment in that the arrangement of the detection coil 410 is different from that in FIG.

  FIG. 13 is a cross-sectional view illustrating an arrangement example of the power reception coil and the detection coil in the modification.

  In FIG. 13, a is a gap provided in a part of the winding of the detection coil 410. B in FIG. 13 is obtained by reducing the number of turns of the detection coil 410 in FIG.

  FIG. 13C shows an example in which the outermost edge of the detection coil 410 is disposed on the track of the power reception coil 430.

  In FIG. 13D, the center of the detection coil 410 is separated from the center of the power receiving coil 430 so that one end of the detection coil 410 is disposed on the track of the power receiving coil 430 and the other is disposed outside the power receiving coil 430. This is a shifted example.

  E in FIG. 13 is an example in which the center of the detection coil 410 is disposed on the track of the power reception coil 430.

  In FIG. 13, the center of the detection coil 410 is separated from the center of the power receiving coil 430 so that one end of the detection coil 410 is disposed on the track of the power receiving coil 430 and the other is disposed inside the power receiving coil 430. This is a shifted example.

  In FIG. 13, g is an example in which the center of the detection coil 410 is shifted from the center of the power reception coil 430 in a range where the detection coil 410 is located inside the power reception coil 430.

  The above-described embodiment shows an example for embodying the present technology, and the matters in the embodiment and the invention-specific matters in the claims have a corresponding relationship. Similarly, the invention specific matter in the claims and the matter in the embodiment of the present technology having the same name as this have a corresponding relationship. However, the present technology is not limited to the embodiment, and can be embodied by making various modifications to the embodiment without departing from the gist thereof.

  Further, the processing procedure described in the above embodiment may be regarded as a method having a series of these procedures, and a program for causing a computer to execute these series of procedures or a recording medium storing the program. You may catch it. As this recording medium, for example, a CD (Compact Disc), an MD (MiniDisc), a DVD (Digital Versatile Disc), a memory card, a Blu-ray disc (Blu-ray (registered trademark) Disc), or the like can be used.

In addition, this technique can also take the following structures.
(1) a measurement coil disposed in the vicinity of a power receiving coil that receives power supplied via a magnetic field;
A measurement unit for measuring the voltage of the measurement coil as a measurement coil voltage;
Foreign matter detection that detects an electrical property value of at least one of the power receiving coil and the measurement coil based on the measurement coil voltage and detects the foreign matter in the magnetic field when the electrical property value is smaller than a predetermined lower threshold value A detecting device.
(2) The foreign object detection unit detects the foreign object when the electrical characteristic value is smaller than the lower limit threshold or when the electrical characteristic value is larger than an upper limit threshold larger than the lower limit threshold. The detection device described.
(3) The detection device according to (2), wherein the upper limit threshold is a value larger than a reference value that is the electrical characteristic value when there is no foreign matter, and the lower limit threshold is a value smaller than the reference value.
(4) The measurement unit further measures the voltage and current of the power receiving coil,
The detection device according to (1) or (2), wherein the foreign matter detection unit acquires the impedance of the power receiving coil as the electrical characteristic value from the measurement coil voltage and the voltage and current of the power receiving coil.
(5) The measurement unit further measures the voltage of the power receiving coil as a power receiving coil voltage,
The detection device according to any one of (1) to (4), wherein the foreign object detection unit acquires a voltage ratio between the measurement coil voltage and the power reception coil voltage as the electrical characteristic value.
(6) The measurement unit further measures the voltage of the power receiving coil as a power receiving coil voltage,
The power receiving coil sequentially receives first and second powers having different power amounts,
The foreign object detection unit acquires a difference between the voltage ratio acquired when the first power is received and the voltage ratio acquired when the second power is received as the electrical characteristic value. The detection device according to any one of (1) to (5).
(7) The detection device according to any one of (1) to (6), wherein the measurement coil has a coil surface area smaller than the power receiving coil.
(8) The detection device according to (7), wherein the measurement coil is disposed inside the power receiving coil.
(9) The detection device according to any one of (1) to (8), wherein the measurement coil is disposed on substantially the same plane as the power reception coil.
(10) The detection device according to any one of (1) to (9), wherein the measurement coil is arranged at a position where a center of the coil surface substantially coincides with the power reception coil.
(11) The power is power fed by a power feeding device,
The detection device according to any one of (1) to (10), further including a transmission unit that transmits a control signal requesting reduction of the amount of electric power to the power supply device when the foreign object is detected. .
(12) a measurement coil disposed in the vicinity of a feeding coil that supplies power via a magnetic field;
A measurement unit for measuring the voltage of the measurement coil as a measurement coil voltage;
Foreign matter detection that detects an electrical property value of at least one of the power receiving coil and the measurement coil based on the measurement coil voltage and detects the foreign matter in the magnetic field when the electrical property value is smaller than a predetermined lower threshold value A detecting device.
(13) a feeding coil for supplying power via a magnetic field;
A power receiving coil for receiving the power;
A measuring coil disposed in the vicinity of the power receiving coil;
A measurement unit for measuring the voltage of the measurement coil as a measurement coil voltage;
Foreign matter detection that detects an electrical property value of at least one of the power receiving coil and the measurement coil based on the measurement coil voltage and detects the foreign matter in the magnetic field when the electrical property value is smaller than a predetermined lower threshold value A power supply system.
(14) a measurement procedure in which the measurement unit measures the voltage of the measurement coil arranged in the vicinity of the power receiving coil that receives power supplied via the magnetic field as the measurement coil voltage;
When the foreign object detection unit acquires the electrical characteristic value of at least one of the power receiving coil and the measurement coil based on the measurement coil voltage and the foreign object detection unit has the electrical characteristic value smaller than a predetermined lower limit threshold value Is a foreign substance detection procedure for detecting a foreign substance in the magnetic field.

DESCRIPTION OF SYMBOLS 100 Power supply apparatus 110 Power conversion circuit 120 Power supply control part 130 Demodulation circuit 140, 454 Impedance matching circuit 150, 420, 440, 441 Capacitor 160 Power supply coil 400, 401 Power receiving apparatus 410 Detection coil 430 Power reception coil 450 Power reception control part 451 Measurement part 452 Modulation circuit 453 Power reception control circuit 455 Rectification circuit 456 Voltage stabilization circuit 457 Load connection circuit 460 Foreign object detection unit 461 Signal processing unit 462 Measurement value holding unit 463 Electrical property acquisition unit 464 Comparison unit 471, 472, 473, 474 Terminal 480 Charge control 481 Secondary battery 482 Load circuit

Claims (14)

A measuring coil disposed in the vicinity of a power receiving coil that receives power supplied via a magnetic field;
A measurement unit for measuring the voltage of the measurement coil as a measurement coil voltage;
Foreign matter detection that detects an electrical property value of at least one of the power receiving coil and the measurement coil based on the measurement coil voltage and detects the foreign matter in the magnetic field when the electrical property value is smaller than a predetermined lower threshold value A detecting device.   The detection device according to claim 1, wherein the foreign matter detection unit detects the foreign matter when the electrical characteristic value is smaller than the lower limit threshold or when the electrical characteristic value is larger than an upper limit threshold larger than the lower limit threshold. .   The detection device according to claim 2, wherein the upper limit threshold is a value larger than a reference value that is the electrical characteristic value when there is no foreign object, and the lower limit threshold is a value smaller than the reference value. The measurement unit further measures the voltage and current of the power receiving coil,
The detection device according to claim 1, wherein the foreign matter detection unit acquires an impedance of the power receiving coil as the electrical characteristic value from the measurement coil voltage and the voltage and current of the power receiving coil. The measurement unit further measures the voltage of the power receiving coil as a power receiving coil voltage,
The detection device according to claim 1, wherein the foreign object detection unit acquires a voltage ratio between the measurement coil voltage and the power reception coil voltage as the electrical characteristic value. The measurement unit further measures the voltage of the power receiving coil as a power receiving coil voltage,
The power receiving coil sequentially receives first and second powers having different power amounts,
The foreign object detection unit acquires a difference between the voltage ratio acquired when the first power is received and the voltage ratio acquired when the second power is received as the electrical characteristic value. The detection device according to claim 1.   The detection device according to claim 1, wherein the measurement coil is a coil having a coil surface area smaller than that of the power receiving coil.   The detection device according to claim 7, wherein the measurement coil is disposed inside the power receiving coil.   The detection device according to claim 1, wherein the measurement coil is disposed on substantially the same plane as the power receiving coil.   The detection device according to claim 1, wherein the measurement coil is disposed at a position where a center of the power receiving coil and a coil surface substantially coincide with each other. The power is power fed by a power feeding device,
The detection device according to claim 1, further comprising: a transmission unit that transmits a control signal requesting a reduction in the amount of electric power to the power supply device when the foreign object is detected. A measuring coil disposed in the vicinity of a feeding coil that supplies power via a magnetic field;
A measurement unit for measuring the voltage of the measurement coil as a measurement coil voltage;
Foreign matter detection that detects an electrical property value of at least one of the power receiving coil and the measurement coil based on the measurement coil voltage and detects the foreign matter in the magnetic field when the electrical property value is smaller than a predetermined lower threshold value A detecting device. A feeding coil that supplies power via a magnetic field;
A power receiving coil for receiving the power;
A measuring coil disposed in the vicinity of the power receiving coil;
A measurement unit for measuring the voltage of the measurement coil as a measurement coil voltage;
Foreign matter detection that detects an electrical property value of at least one of the power receiving coil and the measurement coil based on the measurement coil voltage and detects the foreign matter in the magnetic field when the electrical property value is smaller than a predetermined lower threshold value A power supply system. A measurement procedure in which the measurement unit measures the voltage of the measurement coil arranged in the vicinity of the power receiving coil that receives the power supplied via the magnetic field as the measurement coil voltage,
The foreign object detection unit acquires at least one electrical characteristic value of the power receiving coil and the measurement coil based on the measurement coil voltage, and when the electrical characteristic value is smaller than a predetermined lower limit threshold, the foreign object in the magnetic field And a foreign matter detection procedure for detecting a foreign matter.

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